A biodegradable polyester composition based on a total weight of the biodegradable polyester composition, including a weight content of a cyclic ester compound having a structure shown as formula (I) which is 100 ppm-950 ppm; and based on the total weight of the biodegradable polyester composition, a weight content of tetrahydrofuran is 3 ppm-200 ppm is provided. The cyclic ester compound and tetrahydrofuran is added into the composition and controlling the content of the cyclic ester compound and the content of tetrahydrofuran in a certain range in the composition to realize an anti-thermal oxidative aging property of the biodegradable polyester composition. In addition, a film is prepared by blow molding or a part is prepared by injection molding after being digested with 95% ethanol at 40° C. for 240 hours.